The editing of films and video images, i.e., to rearrange action sequences, is well known. However, the movie and video cameras used to capture the images that are later edited do not store with those images any machine-understandable record of image and camera position. Accordingly, the edited films and videos permit one to view the images in only one predetermined order, determined by the editor. If some other ordering of the image presentation is desired, it must be achieved through a difficult manual editing process.
A computerized, interactive editing process is described in a doctoral thesis "Cognitive Space in the Interactive Movie Map: An Investigation of Spatial Learning in Virtual Environments", by Robert Mohl, 1981, submitted at MIT. In a demonstration carried out using images recorded at Aspen, Colorado, the viewer is permitted to select film clips taken by a camera that is arranged to simulate driving down a street. At each intersection, the viewer chooses to turn left, turn right, or to proceed straight ahead. The viewer thereby simulates driving around streets in Aspen, Colorado.
In other fields, it is known to gather, along with images, information concerning the position of the camera. Governmental and private agencies use satellites and airplanes to record images of positionally referenced data, such as land features or clouds. Each image frame contains positional references to the image tilt or plane of the camera. Present methods commonly either constrain the orientation of the camera to a fixed position, i.e. up and down, or use features captured in the image frames to derive relative positions and orientations of successive images when combining the image frames to form a map or the like.
Devices are known which combine images by matching features common to each of two or more images, i.e. superimposing. These devices must compensate for inevitable distortions of translation and rotation. For example, if an escalator is imaged, and if the images are matched by super-imposing geometric forms (i.e. steps), distorted positional encoding occurs.
Virtual Reality pioneer Jaron Lanier has said that the field of Virtual Reality and computer simulation need a device to collect spatially referenced data for importation into these environments. His term for this device is a "world sucker." The present invention represents one possible way to accomplish this objective.
One aspect of the present invention is recording positional data along with images. A number of methods are known whereby one may locate an object and describe the position of an object relative to a positional reference. For example, a magnetic device is known which can determine its position and orientation within a known magnetic field. Satellite systems and radio signal triangulation can also be used to determine position precisely. Inertial position determination systems are also known and are widely used in inertial navigational --systems.
Inertia describes the tendency of a mass to resist all changes in the direction or magnitude of its velocity that is, the tendency of a mass at rest to stay at rest and the tendency of a moving mass to continue moving in a straight line. Inertial resistance can be used as a means to quantify spatial data, since it has both magnitude and direction.
Gimbals are used in such inertial navigation systems. Gimbals are devices consisting of two rings mounted on axes at right angles to each other, so that an object such as a ship's compass can remain suspended in a horizontal plane between the gimbals regardless of the motion of the ship.
An inertial platform is a system of accelerometers mounted upon an inertial platform supported by gimbals and used in inertial navigation systems. The book Gyroscopes: Theory and Design describes several inertial platforms. This book explains that vehicle accelerations (changes in speed or direction of motion) can be measured by means of accelerometers, each having an axis aligned with coordinate axes of the particular reference frame used by the inertial navigation system. This book explains that special precautions must be taken to maintain continuously proper accelerometer alignment. The book further states "It is necessary therefore, to mount the accelerometers on a gimbaled platform referred to an inertial platform--the orientation of which remains stabilized . . . independent of changes in orientation of the vehicle".
This book explains further that rotation about three axes was recognized as a necessary component of navigation in air space by the Wright brothers, who called rotation about the first axis "roll," rotation about the second axis "pitch," and rotation about the third axis "yaw." This book says that in a three-dimensional inertial navigation system, "the inertial platform must comprise three mutually orthogonal accelerometers and be gyro-stabilized about the roll, pitch, and yaw axes by the action of the separate servos." A servo is a feedback system consisting of a sensing element, an amplifier, and a slave power source that senses the reaction of a gyroscope to twist and that responds by countering the twist to stabilizing the inertial platform.
A "two-degree-of-freedom" gyro is one which can sense angular motion of the platform about two axes simultaneously, thereby enabling only two gyros to stabilize an internal platform about three axes. Mathematical equations for calculation of corrections for gravitational acceleration are included in the above book.
Chapter 7 of Inertial Navigation Systems by Charles Boxmeyer, McGraw-Hill, 1964 is entitled "Some Inertial-navigation-system Designs." This chapter discusses a variety of assemblies of components designed to solve various inertial-navigation problems. It describes the transformations that are necessary to recover true inertial frame acceleration information from an attitude-sensed arrangement of accelerometers which are not gimbaled. One system described has two accelerometers mounted on a gimbaled platform: one is mounted upon the azimuth (yaw) axis, to measure roll and pitch; and the second is mounted normal (perpendicular) to the azimuth axis. The platform includes three gimbals. Another system described provides five gimbals for roll, pitch, azimuth, latitude, and longitude. A third system described provides no torquing signal to the gyro with an azimuth axis. This system allows for a single fixed (vertical) orientation. Another system described forces the accelerometer input axes into a preferred alignment with respect to the earth. It is a four-gimbal system where the innermost gimbal is maintained non-rotational by means of three integrating gyroscopes all of which are mounted upon the fourth gimbal, and three accelerometers are mounted upon the stabilized inner platform.
At one point, this chapter says: "If the gyros and accelerometer are mounted directly to the frame of a vehicle, and the stable table dispensed with, it is obvious that a considerable saving in size and weight would result. It is also obvious that the transformation theory that has been used previously could be extended to apply to this case and that position and velocity could be computed by performing operations on the gyro and accelerometer outputs. The physical indications of north, east, and the vertical would not be available, but information would be available in the form of computer outputs referring these directions to the vehicle frame. "A difficulty with this procedure is that the rapid motion of the vehicle in roll, pitch, and yaw would subject the gyros to angular-rate inputs over a much greater range than . . . [they] encounter when they are mounted on the gimbals of a stable table, . . . . Since the gyros are forced to have the same angular velocity as the vehicle, they must be connected as rate gyros....
Assuming, however, that the sensing components have sufficient accuracy to make the mechanization of such a system a worthwhile enterprise, we proceed to discuss the design of a system using three accelerometers and three gyros which are mounted directly on the frame of the vehicle."
A satellite global positioning system based ground video mapping system is described in GPS WORLD, February, 1994, which states "Using two vans equipped with video cameras, computers, and an integrated system of GPS, inertial, and wheel-turn sensors for positioning, Global Visions provides drive by digital maps."